1. Field of the Invention
The present invention relates to a lamp device and a method of bonding a mirror reflector to the lamp and, more particularly, to a structure obtained by bonding the mirror reflector and the lamp and a method of injecting an adhesive.
2. Description of the Related Art
A lamp with a mirror reflector is used in a light source unit of a cineprojector, a general projector, or the like.
In order to illuminate articles at shores with beam spots, lamps with mirror reflectors have been used as light sources for so-called "spot down lights".
A lamp with a mirror reflector used in such a field, i.e., a field of article illumination, has an integral structure obtained by bonding the mirror reflector to the lamp.
The reflector comprises a reflector body made of glass or a metal and a dichroic film formed on the inner surface of the reflector body.
The reflector body has a reflector axis and a curved surface. The curved surface is, for example, a surface of second degree having the reflector axis as its center of revolution. The surface of the second degree is, for example, an ellipsoidal or paraboloidal surface of revolution. A front-surface light projection portion is located at a front end portion of this curved surface, and a lamp mounting portion is located at its rear end portion. The lamp mounting portion comprises a cylinder having a hollow structure and extends backward from the quadratic surface of revolution.
The dichroic film is formed on the inner surface of the curved surface of the reflector body and has an optical interference function of reflecting visible light rays and transmitting infrared rays.
The lamp comprises, for example, a halogen lamp. This lamp comprises a bulb made of quartz glass and a filament made of a tungsten coil arranged inside the bulb.
A sealing portion having a pinch seal structure is formed at one end portion of the bulb. Metal foils made of molybdenum are sealed on the pinch sealing portion. Inner and outer wells are respectively connected to these metal foils. The inner wells are connected to the filament stored in the bulb, and the outer wells are guided outside the bulb from the end portion of the sealing portion. The outer wells are then connected to terminal pins outside the sealing portion.
The lamp having the above structure is bonded to the reflector body by an adhesive. The adhesive can be a heat-resistant inorganic adhesive (inorganic cement) having a metal oxide such as alumina, silica, magnesia, or zirconia as a major constituent. This adhesive is filled between the outer surface of the lamp sealing portion of the curved surface and the inner surface of the lamp mounting portion while the sealing portion of the lamp is inserted into the hollow portion of the lamp mounting portion. Therefore, the adhesive can bond the lamp sealing portion to the lamp mounting portion of the mirror reflector.
By this bonding operation, the lamp is located inside the reflector body such that the center of light emitted from the filament is almost aligned with a focal position of the reflector.
In the lamp with a reflector having such a structure, when the terminal pins are electrically connected to a power source, a current flows through the filament, and light is emitted from the filament.
Light emitted from the filament passes through the bulb and reaches the dichroic film formed on the curved surface of the reflector body. Visible light of the light having reached the dichroic film is reflected by this film, and infrared rays having a wavelength of about 700 nm or more are transmitted through the dichroic film.
The visible light reflected by the dichroic film is projected forward from the light projection portion and illuminates objects such as articles. Light emitted from the lamp with the reflector contains only a small amount of heat, and temperatures of the objects such as articles are not increased, thereby preventing the objects from being adversely affected by heat.
When the filament emits light, it is heated. Heat from the filament is conducted to the sealing portion through the inner wells. The temperature of the sealing portion is increased. Infrared rays emitted from the filament cause an increase in temperature of the bulb wall. Heat from the bulb wall is conducted to the sealing portion to increase the temperature of the sealing portion.
When the dichroic film is formed o the reflecting surface as in the conventional lamp with a reflector, the infrared rays having passed through the dichroic film by the optical interference of the dichroic film reach the mirror reflector body to increase the temperature of the reflector body. Heat from the reflector body is conducted to the lamp mounting portion of the reflector. This heat is then conducted to the lamp sealing portion through the adhesive filled between the inner surface of the lamp mounting portion and the outer surface of the lamp sealing portion.
The temperature of the sealing portion is excessively increased to cause a thermal stress.
The following conventional method is used to bond the lamp to the reflector.
In the conventional method, the lamp is inserted into the reflector from the front opening of the reflector so that the sealing portion of the lamp passes the opening first, so that the sealing portion is inserted into the lamp mounting portion. The central axis of the lamp is aligned with the center line of the reflector, and at the same time the center of emission of the lamp is located at the focal point of the reflector. The reflector and the lamp are maintained in this state.
In this state, an operator holds an adhesive injection nozzle and inserts it into the lamp mounting portion from the front opening of the reflector. The adhesive i then injected from the injection nozzle and is filled in a space between the sealing portion of the lamp and the lamp mounting portion of the reflector.
In order to entirely fill the adhesive in the space between the sealing portion of the lamp and the lamp mounting portion of the reflector, the adhesive is injected at two positions in the space between the sealing portion and the lamp mounting portion.
When the adhesive injection operation is completed, the adhesive is dried and hardened.
In the conventional method described above, since the adhesive injection nozzle is held by the operator and is inserted into the space in the mounting portion through the front opening of the reflector, the adhesive may leak from the tip of the injection nozzle during its insertion, and this adhesive droplet may be attached to the reflecting surface.
In particular, when the adhesive is to be injected into the space between the sealing portion and the lamp mounting portion, the adhesive is filled twice, i.e., at two positions in the entire space. When the injection nozzle is pulled out from one position of this space and is then inserted into another position of the space, the adhesive tends to leak from the tip of the injection nozzle, and the resultant droplets may be attached to the reflecting surface.
When the adhesive is attached to the reflecting surface even in a very small amount, the reflecting surface is contaminated to degrade the reflecting performance. Therefore, the attached adhesive must be immediately removed from the reflecting surface.
Since a distance between the front opening and the lamp mounting portion is long to make it difficult to insert the adhesive injection nozzle and the distance between the sealing portion and the mounting portion of the lamp is small, the method of inserting the adhesive injection nozzle from the front opening of the reflector results in poor adhesive supply efficiency and disables automatic adhesive filling.